In the springtime large parts of the populations of Central, Eastern and Northern Europe, America and Australia suffer from allergic symptoms (rhinitis, conjunctivitis, dermatitis and pollen asthma). Proteins which can be isolated from pollen of trees of the order Fagales, in particular from pollen of birch, alder, hazel, hornbeam and oak, are responsible for most of these allergic symptoms (1).
At least 10% of the population suffers from pollen allergies at various times and to varying extent. These allergies are mediated by IgE antibodies which react with pollen proteins. The possibility exists for a therapy for pollen allergies by hyposensitization, i.e., by the regular and slowly increasing administration of the proteins producing the allergy.
Diagnostic methods for allergic diseases, such as RIA (radioimmunoassay), IRMA (immuno-radiometric assay), RAST (radio-allergosorbent test), ELISA (enzyme-linked immunosorbent assay), magnetic allergoabsorbent test, immunoblots, LIA (luminescence immunosay), histamine release assays and others depend greatly upon the availability of pure allergens. Protein extracts from pollen isolated from natural sources are difficult to standardize because preparations vary from batch to batch. For example, they may contain unwanted constituents, and/or certain proteins may be lost in the extraction procedure and be missing from the final separation (2). Clearly, diagnostic tests which employ well defined allergens that can be reproducibly prepared would be superior to tests which employ raw pollen extracts with an insufficiently defined mixture of allergens and other components. Recombinant DNA production of allergenic polypeptides, or allergenic fragments thereof, would allow more reprodicible preparations of allergens of defined content for standardized diagnostic and therapeutic methods.
Allergens may be purified to homogenity from pollen by known protein/chemical methods, for example, by means of affinity chromatography (3). These methods are relatively costly and require pollen as an ill-defined source which cannot be standardized. It would, therefore, be cheaper and more efficient to use recombinant DNA methods to produce an allergenic protein, or fragments of that protein.
Hyposensitization has proved to be an effective therapy in allergic diseases. This therapy consists of parenteral or oral administration of allergens in increasing doses over a fairly long period of time. Like diagnostic methods, it requires pure and well defined allergens. The use of purified recombinant allergens or synthetic peptides would greatly reduce the risk of sensitizing patients to unwanted components.